1. Field of the Invention
The present invention generally relates to a display, and in particular, to a multi-domain vertical alignment liquid crystal display (MVA-LCD).
2. Description of Related Art
Currently, thin film transistor-liquid crystal displays (TFT-LCDs) with high contrast ratio, no gray scale inversion, high brightness, high color saturation, quick response, and wide viewing angle, etc are required by the market. The common wide viewing angle techniques includes TN displays with wide viewing film, in-plane switching (IPS) LCD, fringe field switching (FFS) LCD, and multi-domain vertical alignment (MVA) LCD. For example, the MVA LCD panel uses some alignment patterns, such as alignment protrusions or the slits to make liquid crystal molecules in each pixel being arranged in multi-direction, thereby obtaining multiple different aligned domains. The conventional MVA LCD panels, due to the alignment protrusions or slits formed on the color filter substrate or the TFT array substrate can make the liquid crystal molecules being arranged in multi-direction, thereby obtaining multiple different aligned domains, thus meeting the requirement for wide viewing angle.
FIG. 1 illustrates the relationship between the normalized transmittance and the gray level of a conventional MVA-LCD with a circular polarizer. A conventional MVA-LCD usually has a circular polarizer because the circular polarizer has higher transmittance and accordingly the brightness of the LCD panel can be increased. The relationship between the normalized transmittance and the gray level of the conventional MVA-LCD having the circular polarizer is referred as a gamma curve. Referring to FIG. 1, the abscissa indicates gray level and the ordinate indicates normalized transmittance. As shown in FIG. 1, even though the conventional MVA-LCD can achieve a wide viewing angle, the gamma curve has different curvatures along with the changes of the viewing angle. In other words, when the viewing angle changes, the brightness displayed by the conventional MVA-LCD also changes, so that the problem of color shift or color washout may generate.
Various conventional techniques have been provided for resolving the problem of color shift or color washout. One of the methods is to form an additional capacitor in each single pixel unit, such that different electric fields can be produced through capacitance coupling between different pixel electrodes in each single pixel unit, respectively, and therefore the liquid crystal molecules above the different pixel electrodes can have different orientations. However, in this method, the display quality of the LCD may be deteriorated due to the RC delay effect even though color shift is reduced.
Another method is to dispose an additional transistor in each pixel unit. In other words, each single pixel unit has two transistors. With these two transistors, two pixel electrodes in the single pixel unit produce two different electric fields so that the liquid crystal molecules above the pixel electrodes have different orientations and accordingly color shift is reduced. However, in this method, a single pixel unit has two transistors and the number of scan lines or data lines for controlling the transistors increases accordingly, and therefore both the complexity and the fabricating cost of the driving circuit are increased.
However, when the foregoing conventional techniques are applied to a conventional LCD, even though the problem of color shift can be resolved, the brightness of the conventional LCD is reduced due to the reduction in the aperture ratio thereof.